Ask in chat if there are some other high level players in the area to help you out with the opposing faction. LocalDefense will bring in nearby players; also consider asking your guild. You can also go to Northfold Manor; often there are fewer players there, and it is usually forgotten by high-level griefers. Or come back at another time of day when it’s less crowded. I had to make this video in the middle of the night, and still ran into a couple of other players.

Several users have asked what to do when you accept the Battle for Gilneas City quest and the prince does not appear on the bridge. This happens when a battle is already in progress. You can run in and join the battle in progress, or wait for the event to end and start a fresh one. I recommend waiting, since you may have to fight your way through leftover mobs to join the battle, and you may miss the end of the event and fail to get quest credit.